Device and method for forming a plasma by application of microwaves

Abstract

A device for forming a microwave plasma including an ionizing chamber wherein a gas can be introduced so as to undergo excitation induced by the presence of a high frequency alternating electric field produced by a plurality of metal antennas. The device includes a gas-free volume wherein metal antennas are arranged parallel to one another and are distributed at the nodes of a regular plane array, an end of each antenna extending from the gas-free volume in the ionizing chamber and an induction loop producing microwaves in the gas-free volume.

We claim: 
     
       1. A device for forming a plasma from microwaves comprising an ionization chamber including a gas-free volume into which a gas can be introduced to undergo excitation due to the presence of a high-frequency alternating electrical field emitted by a plurality of metal antennas disposed in said ionization chamber, wherein said metal antennas are disposed parallel to each other and distributed at nodes of a regular plane network, one end of each antenna extending outside said gas-free volume in the ionization chamber, with at least one induction loop emitting microwaves into the gas-free volume. 
     
     
       2. The device according to claim 1, wherein said microwaves have a wavelength and a length of the metal antenna is approximately an odd multiple of a quarter of the wavelength of the microwaves in a vacuum. 
     
     
       3. The device according to claim 1, further comprising means for generating a polarization electrical field in the gas-free volume, wherein the field is able to concentrate ions formed in the vicinity of the metal antennas as an ion sheath. 
     
     
       4. The device according to claim 3, wherein the means for generating the polarization electrical field includes the metal antennas that serve to apply the microwaves in the plasma. 
     
     
       5. The device according to claim 1, further comprising a single induction loop for application of the microwaves in the gas-free volume. 
     
     
       6. The device according to claim 1, further comprising permanent magnets able to generate a static magnetic field in the ionization chamber. 
     
     
       7. The device according to claim 6, wherein the metal antennas comprise hollow tubes and the permanent magnets are placed inside the metal antennas and the permanent magnets comprise axially supplied bars. 
     
     
       8. A method of forming plasma for microwaves comprising using a device for forming a plasma from microwaves comprising an ionization chamber including a gas-free volume into which a gas can be introduced to undergo excitation due to the presence of a high-frequency alternating electrical field emitted by a plurality of metal antennas disposed in said ionization chamber, wherein said metal antennas are disposed parallel to each other and distributed at nodes of a regular plane network, one end of each antenna extending outside said gas-free volume in the ionization chamber, with at least one induction loop emitting microwaves into the gas-free volume. 
     
     
       9. The method according to claim 8, further comprising adding a quasi-static polarization electrical field to the electrical field to concentrate ions around each of the metal antennas.